1. Field of the Invention
The invention relates to a drive device, especially for displacement of the sliding roof of a motor vehicle, with an electric motor, gearing driven by the electric motor, and a circuit for triggering the electric motor.
2. Description of Related Art
A drive device of the initially mentioned type is described in U.S. Pat. No. 6,162,142. Here, in particular, a drive device for a motor vehicle roof is proposed in which rotation of the driven shaft of the electric motor is tapped by means of a worm gear pair which is held in contact with the driven shaft by means of a housing which surrounds both the driven shaft and the worm gear pair. Furthermore, the housing has a housing area which is laterally offset next to the worm gear pair and in which there is a board on which there are components for triggering the drive motor. The individual assemblies, especially the driven shaft and the worm gear pair which is driven by the driven shaft are not shielded relative to the board so that there is the danger that ordinarily lubricant which is provided between the driven shaft and the worm gear pair can leak onto the board and the components located on it; this can lead to an adverse effect on the function of these components.
Additionally, U.S. Pat. No. 5,768,942 discloses a drive for a motor vehicle roof in which the reducing gear and electrical circuit are accommodated in separate housing parts which are detachably joined to one another to enable flexible matching to different circuit layouts. The gear housing part is produced as a metal die casting and the electric housing part as an injection molded plastic part.
A primary object of this invention is to devise a drive device of the initially mentioned type which has a compact structure and in which reliable operation of the device is ensured even over long and intense periods of use.
This object is achieved in a drive device of the initially mentioned type in that the gearing is accommodated in a gear casing with at least one casing wall of high thermal conductivity and at least part of the circuit is located adjacent to this casing wall outside the gear casing. Furthermore, contact between the components of the circuit and the casing wall acts to dissipate the heat which forms during operation of the circuit to the casing wall.
In this way, an inherently closed drive device with an electric motor, gearing driven by the electric motor and a circuit for triggering the electric motor is made available, in which these assemblies can be located extremely compactly, especially in a common housing, but the gearing being accommodated in a separate gear casing so that the lubricant which is ordinarily used in these casings cannot reach the circuit and thus adversely affect operation of the electronic circuit for triggering the electric motor. Furthermore, the use of the casing wall of the gear casing as a cooling surface for components of the circuit makes it possible not only to build the drive device smaller overall, and thus more compact, since additional cooling volume need not be made available, but makes it possible to accommodate the drive device in plastic housings which are lighter and easier to produce compared to the metal die cast housings used in the past, and which to date due to their thermal conductivity which is low compared to metal housings were problematical with respect to overheating of the circuit components located in them.
Other embodiment and features are described in detail below. For example, contact of the circuit or of its components with the casing wall can be made using any means which are good conductors of heat, but which are at the same time electrical insulators. Examples of these contact-making means are cooling lugs assigned to the circuit, as well as thermally conductive foils which are located between the circuit and the casing wall, whether in the form of a filler or as individual lugs which are applied to the individual components to be cooled, for example cemented, or thermally conductive foam or fiber bodies located between the circuit and the casing wall, for example, made of thermally conductive, electrically insulating material or in the form of a composite which is composed of a thermally conductive, electrically conductive fiber material, for example, aluminum fibers, and an insulator layer which is applied to one side or both sides.
Preferably, the circuit is accommodated in an electronics housing which is at the same time part of the gear casing. Here, the electronics housing can have a lower part which is, at the same time, part of the gear casing, and a cover. Furthermore, the gear casing can be formed by a wall surface of the electronics housing, a side wall connected integrally to the wall surface, and a cover which is seated on the side wall and which preferably seals the gear casing closed. To keep the weight of the drive device as low as possible, the electronics housing and the gear casing which is preferably at least partially integrated with it can be produced from plastic, to make available a cooling surface for components of the circuit for triggering the electric motor, the cover being made of a metallic material with which the components to be cooled are in contact.
In another embodiment of the invention, the electric motor can have a pole shaft which is located in the shaft housing and which is drive-connected to the gearing. In the same manner in which the electronics housing and the gear casing are preferably at least partially integrated, feasibly the shaft housing is also at least partially integrated into the electronics housing.
An especially compact and still easily accessible drive device arises when the electronics housing has a lower part into which both the gear casing and the shaft housing are integrated, the gear casing and the shaft housing being formed by a wall surface of the electronics housing, a side wall which is connected in one piece to this wall surface, and a preferably common cover which is seated on the side wall, and the electronics housing, furthermore, having a cover which can be placed on the lower part and which preferably has means for locking the circuit.
The (partial) integration of the gear casing and the shaft housing into the electronics housing yields an extremely compact drive device in which the mutual integration of the individual housing sections saves not only material, and thus weight, but at the same time, also increases the stability of the entire device, especially when the lower part and the cover of the electronics housing are each one-piece shaped components in which, then, the subdividing walls, i.e., the side wall of the gear casing and the side wall of the shaft housing, are used at the same time as reinforcements of the entire arrangement.
One preferred embodiment of the drive device proposed here is detailed below with reference to the attached drawings.